Adjustable support for drafting table



May 2, 1961 E. H. MAY

ADJUSTABLE SUPPORT FOR DRAFTING TABLE 2 Sheets-Sheet 1 Filed Oct. 16, 1958 May 2, 1961 E. H. MAY

ADJUSTABLE SUPPORT FOR DRAFTING TABLE 2 Sheets-Sheet 2 Filed Oct. 16, 1958 Uflitfi States P t 9 ADJUSTABLE I SUPPORT FOR DRAFTING TABLE Ellwood H, 'Mayisheboygan, Wis, assign'or to Mayline Company, Inc., a corporation of Wisconsin Filed Oct. 16, 1958, Ser. No. 767,713

7 Claims. ems-131 justable drafting board support including a pair of 'vertically' pivoted links for elevating and lowering. the

board and having a novel counterbalancing arrangement which is adjustable toaccommodatediiferent work loads on the boardgl i v Stillanother object of this invention is to provide an improved apparatusfor locking'the drafting'board in any preselected adjusted position thereof.

"Ihese, together with various ancillary objects and advantages of this invention will bemore readily appreciated as the same becomes better understood. by reference to the following. detailed description when taken in connection with the accompanying drawings wherein:

Figure l is afragmentary perspective view of the drafting table with parts broken away to illustrate details of construction; f

' Fig. 2 is an enlarged fragmentary view of the apparatus fora'djustably connecting the. counterbalancing spring to the elevating and lowering links;

Fig. 3 is an'enlarged fragmentary sectional view taken on the plane 3-3 of Fig. 2; v v

Fig. 4 is a fragmentary side elevational' view of the tablewith the side panel rern'oved and illustrating the drafting board in its raised position; t I

Fig. Sis an enlarged fragmentary horizontal sectional view illustrating the locking mechanism for the table; a

and v t Fig. 6 is an enlarged fragmentary sectional view taken on the plane 6-6 of Fig. 5.

The'drafting table in'general includes a base having upstanding side panels 10, a top 11 extending between the sidejpanels and one or more shelveslz disposed below the top 11. Support legs 13 are provided 'at the lower ends of the side panels to support thesame in spaced relation to'the floor. The drafting board 15 is mounted on the base for vertical adjustment with respect thereto and also for limited lateral tilting movement and, as shown herein, the drafting board includes a sheet metal top 16 having. a depending peripheral flange 17. A plurality of longitudinally extending reinforcing channels 18 are afiixed, as by'welding to the underside of the top to rigidify the same. Thechannelmembers are attached to angle iron cross members 19. at oppositesides of the base, which cross members 'are pivotally mounted by means of generally triangularly shaped brackets21 on the vertically adjustable support posts 22. 'The brackets 21 are pivotally attached to the posts by means of Patented May 2, 1961 fasteners 23 and a locking mechanism, including an arcuate bar 25 and a locking block 26 to be described more fully hereinafter, is provided for locking the drafting board in any preselected inclined position. As best shown in Fig. 4, each arcuate bar'25 is terminally attached by fasteners 27 and 28 to the post 22 and the locking block 26 is supportedin the bracket 21 and receives the arcuate bar 25.

The post 22 is conveniently formed in two telescoping sections 22a and 22b, of channel shaped configuration, and which are secured together by fasteners 29. A channel shaped tie rail 31 extends between the lower sections 22a of the support posts to rigidly interconnect the same and the lower sections are vertically adjustably supported on upper and lower links 32 and 33 attached to the base. I

In particular, the upper and lower links are attached to an upright frame including generally L-shaped top and bottom members 35 and 36 having one flange thereof secured to the side panels 10 of the base. A first upright rail 39 extends between the top and bottom members 35 and 36 adjacent one end thereof and has one flange 39a disposed adjacent the side panels llland a second flange 39b spaced laterally from the side panels to receive the links 32 and 33 therebetween. Ihe upper links 32 at opposite sides of the base are pivotally mounted on the flange 39b by means of a rigid rod 41 which is secured thereto, as by welding, and extends therebetween to cause the upperlinks to move in unison ,with each'other. The lower links 33 are pivotally supported on the flange 396 by bolts 42. A second upright rail 43 extends between the top'and bottom members and 36 adjacent the other end thereof and has a first flange 43a laterally offset from the panel 10 to receive the links 32 and 33 therebetween and a second flange 43b which islaterally offset from the first flange in a direction away from the panels 10. The free ends of the links 32 and 33 are pivotally connected by means of fasteners 45 and 46 to the lower section 22b of the respective support post. A

channel shaped cross rail 48 extends betweenthe upright rails 43 at opposite sides of the base and underlies the top 11 thereof to support the same as is clearlyshown inFig. 4.

In accordance with the present invention; an improved spring type counterbalance is provided for the drafting board 15 to facilitate elevating and lowering the board. In general, the spring is operatively connected vto'th'e upright frame on the base and 'to' the lower link and is so arranged as to maintain a substantially" constant lift on the drafting board as the same is elevated, notwithstanding the decrease in tension in the spring as the table moves upwardly. In addition, provision is made for adjusting the weight which the counterbalancingrspringwill support so as to accommodate additional equipment such as a drafting machine carried by the board 15.

An elongated coil type tension spring 51.is provided and has a rod 52 threaded into a fitting'53" at the upper end thereof. The rod extends through an opening 54 in the top member 35 and is supported thereon by means of a ball member 56 non-rotatably attached to the upper end of the rod to permit limited swiveling movement of the spring. The rod 52 is threadable into the fitting 53 on the spring to permit initial adjustment .of the spring tension. The lower end of the spring 51 has the hook 5 8 thereon which is operatively connected to the lower link- 33 to normally urge the same to its raised position shown in solid lines in Fig. 4.

As is apparent, when the links move from their lowered position shown in Fig. 1 and also in phantom in 'Fig. 4, to the raised position shown in solid lines in board is movedtowarditsraised position, an arm 61 is attached to the lower link 33 ate point'spaced 'fromthe pivot point 42 thereof, which arm extends downwardly below the lower link an appreciable distance. As shown herein, the length of the arm -6 1fis approximately equal to the spacing between the arm and the -pivotpoint 42 of the lower link. The'hook 58 "on the lower end of the spring '51 is attached to'the'freeend of 'thearm 61.

When the link 33 is in its lowered position shown in Fig. 1 and in phantom in Fig. 4, the spring 51 crosses the lower link at a point spaced relatively closely to the pivot point 42 of the lower link. As the lower link moves upwardly, the point at which the spring 51 crosses the lower link 3'3 moves outwardly away from the pivot point -42 thereof and-thus increasesthe elfective distance between the spring and the pivot point of the lower link. Thug-while the force or tension exerted by the spring 51 decreases as the link 33 moves upwardly, the eifective distance between the spring 51 and the pivot point of the lower link is increased so as to thereby compensate for the decrease in spring tension and maintain a substantially uniform lift on the drafting board.

In order to accommodate ditferent weights on the drafting board, as may be caused by the mounting of a drafting machine thereon, provision is made for adjusting the point of attachment of the lower end of the spring 51 in a direction longitudinally of the lower'link to thereby increase the-effective distance between the spring and the pivot point of the lower link, in all operative positions of the latter. As shown herein, the arm 61 is made channel shaped in cross-section and has flanges 6111 along oppositesides thereof. A lead screw 67 is rotatably supported-in the flanges 61a and extends generally parallel to' the lowerarm 33. .The lead screw has a socketed head 68 on one end to enable turning of a screw with a suitable wrench, and nuts 69 are provided on the other end of the screw to retain the same in assembled relation on the arm. A follower comprising a plate 71 having laterally extending cars 72 is mounted on the screw '67 and moves therealong as the screw is rotated. A guide slot 73 is formed in the arm in parallel relation to the screw 67 and a guide'block 74 is slidably supported in the slot and attached to the plate 71 of the follower by means of a socketed screw 76. An opening 77 is provided in the guide block for receiving the hook 58 of the spring whereby adjustment of the follower along the arm effects adjustment of the lower end of the spring 51. As is apparent, the socketed screw 76 is loosened before turning the lead screw 67 to adjust the follower, and the screw 76 is thereafter tightened to clamp the guide block :74 in its adjusted position'on the arm.

The drafting board 15 is locked in any preselected vertically adjusted position thereof by means of a locking rod 81 which is swingably attached by a fastener '82 :to the upper link 32'. The locking rod extends downwardly from the upper link alongside the upright rail '53 and through alocking block 84 mounted on that rail. More particularly, a tubular sleeve 85 is rotatably supported in the leg 43b of the upright rail 43 and conistrained against axial movement by a collar 86 secured to the sleeve by a set screw 87. The sleeve has diametrically opposed slots 88 (see Figs. 5 and 6) which open atoneend thereof and loosely receive an elongated fiat locking block 84. The locking block is retained in assembled relation on the sleeve by a pin 89 attached to the sleeve and which loosely extends through an opening 91 in the block to permit limited lateral shifting of the block relative to the sleeve.

Theblock 84 has an enlarged opening 92 having a diameter larger than the rod 81 and which slidably receives the same. Semi-circular recesses are formed at diametrically opposedsides of the opening 92 to form cusps or points 93 which are arranged to engage the rod 81 when the'elock is t'ilted'to lock the rod against movement. 'I'helocking blocks at opposite sides of the base are interconnected by a tube 95 and a pin 96 extends through :the sleeve and tube 95 to'secure the "same in "assembled relation. A spring '97 is attached to the outer end of the pin 96 and to the base of the drafting table to yieldably tilt the block in one direction and effect locking of the rod 81 against movement. A lever 98, herein shown of a foot operated type, is attached to the tube 95 to permit manual release of the locking blocks 84. The locking block 26 provided on the arcuate 'bar 25 for the table tilt mechanism is of the same construction and further detailed construction is deemed unnecessary.

From the foregoing it is apparent that the counterbalancing mechanism is arranged to maintain a substantially constant lift forthe drafting board so that the same can be moved from its lowered position to its raised position with very little elfort. Moreover, the counterbalance can be adjusted by shifting the point of attachmeant of the lower end of the spring511in a direction parallel to the link 33 sov as to accommodatejdifferent loads on'the drafting table. Sincethe locking blocks'84 and 26 are mounted for limited lateral movement, these blocks can shift and'prevent binding between'the'respective rods and the locking blocks due to slight misalignmeuts thercbetween. When rclease'd, the blocks are'tilted and the cusps or corners 93 engage the respective rods to lock the same against movement.

I claim:

1. In a drafting table including a base having an upright frame 'section, a'drawing board, a parallelogram type linkage for supporting the board on the base for vertical adjustment with respect thereto *comprising upper and lower parallel links mounted on said upright frame section for vertical pivotal movement relative thereto, a post pivotally attached to the free ends of said links to remain upright as said links swing from .'an upper to a lower position, means attaching said drafting board to said post, a tension spring for counterbalancing said board, said tension spring having the upper end thereof attached to said upright frame section and extending downwardly therefrom generally crosswise of said links, andmeans operativelyconnectingthe lower end of said spring to said .lower link to elongate and contract the spring as the links swing respectively downwardly and upwardly, said means including .an arm attached to the lower link and extending downwardly therefrom, and means attaching the lower end of s'aidspring to said arm at an appreciable distance below thelongitudinal axis of said lower link suflicient .to cause the point at which said spring crosses the lower link shift away from the pivot point of the lower link on 'said support as the link swings upwardly an amount to substantially compensate for the. decrease in spring tension as the spring contracts.

2. In a drafting table including a base having an upright frame section, a drawing board, a parallelogram type linkage for supporting the board on the base for vertical adjustment with respect thereto comprising upper and lower parallel links mounted on said upright frame section for vertical pivotal movement relative thereto, a post pivotally attached to the free ends of said links to remain upright as said links swing from an upper to a lower position, means attaching said drafting boardto said post, a tension spring 'forcounterbalancing said board, said tensionspring having the upper end thereof attached to said upright frame section and extending downwardly therefrom generally crosswise of said links, and means operatively connecting the lower end of said spring to said lower link to elongate and contract the spring as the links swing respectively downwardly and upwardly, said last mentioned means including means for adjusting the point of attachment of said spring to said lower link in a direction toward and away from the pivot point thereof to accommodate different loads on said drafting table.

3. In a drafting table including a base having an upright frame section, a drawing board, a parallelogram type linkage for supporting the board on the base for vertical adjustment with respect thereto comprising upper and lower parallel links mounted on said upright frame section for vertical pivotal movement relative thereto, a post pivotally attached to the free ends of said links to remain upright as said links swing from an upper to a lower position, means attaching said drafting board to said post, a tension spring for counterbalancing said board, said tension spring having the upper end thereof attached to said upright frame section and extending downwardly therefrom generally crosswise of said links, and means operatively connecting the lower end of said spring to said lower link to elongate and contract the spring as the links swing respectively downwardly and upwardly, said means including an arm attached to the lower link and extending downwardly therefrom, and means attaching the lower end of said spring to said arm for adjustment with respect thereto along a path parallel to and laterally offset an appreciable distance below said lower link.

4. In a drafting table including a base having an upright frame section, a drawing board, a parallelogram type linkage for supporting the board on the base for vertical adjustment with respect thereto comprising upper and lower parallel links mounted on said upright frame section for vertical pivotal movement relative thereto, a post pivotally attached to the free ends of said links to remain upright as said links swing from an upper to a lower position, means attaching said drafting board to said post, a tension spring for counterbalancing said board, said tension spring having the upper end thereof attached to said upright frame section and extending downwardly therefrom generally crosswise of said links, and means operatively connecting the lower end of said spring to said lower link to elongate and contract the spring as the links swing respectively downwardly and upwardly, said means including an arm attached to the lower link and extending downwardly therefrom, a lead screw mounted on said arm and paralleling said lower link, a follower on said screw movable parallel to said lower link as the screw is rotated, and means attaching the lower end of said spring to said follower for movement therewith.

5. In a drafting table including a base having an upright frame section, a drawing board, a parallelogram type linkage for supporting the board on the base for vertical adjustment with respect thereto comprising upper and lower parallel links mounted on said upright frame section for vertical pivotal movement relative thereto, a post pivotally attached to the free ends of said links to remain upright as said links swing from an upper to a lower position, means attaching said drafting board tosaid post, a tension spring for counterbalancing 6. In a drafting table including a base having an upright frame section, a drawing board, a parallelogram type linkage for supporting the board on the base for vertical adjustment with respect thereto comprising upper and lower parallel links mounted on said upright frame section for vertical pivotal movement relative thereto, a post pivotally attached to the free ends of said links to remain upright as said links swing from an upper to a lower position, means attaching said drafting board to said post, a tension spring for counterbalancing said board, said tension spring having the upper end thereof attached to said upright frame section and extending downwardly therefrom generally crosswise of said links, and means operatively connecting the lower end of said spring to said lower link to elongate and contract the spring as the links swing respectively downwardly and upwardly, said means including an arm attached to the lower link and extending downwardly therefrom, flanges along opposite sides of said arm extending transverse thereto, a lead screw supported in said flanges for rotation about an axis parallel to and laterally offset below said lower link, said arm having a guide slot therein paralleling said lower link, a follower mounted on said screw and extending through said slot, and means attaching the lower end of said spring to said follower for adjustment therewith.

7. In a drafting table including a base having an upn'ght frame section, a drawing board, a parallelogram type linkage for supporting the board on the base for vertical adjustment with respect thereto comprising upper and lower parallel links mounted on said upright frame section for vertical pivotal movement relative thereto, a

- post pivotally attached to the free ends of said links to said board, said tension spring having the upper end 7 thereof attached to said upright framesection and extending downwardly therefrom generally crosswise of said links, and means operatively connecting the lower end of said spring to said lower link to elongate and contract the spring as the links swing respectively downwardly and upwardly, said last mentioned means including a lead screw paralleling said lower link, a follower on said screw movable parallel to said lower link as the screw is rotated, and means attaching the lower end of said spring with.

to said follower for movement thereremain upright as said links swing from an upper to a lower position, means attaching said drafting board to said post, a tension spring for counterbalancing said board, said tension spring having the upper end thereof attached to said upright frame section and extending downwardly therefrom generally crosswise of said links, and means operatively connecting the lower end of said spring ,to said lower link to elongate and contract the spring as the links swing respectively downwardly and upwardly, said means including an arm attached to the lower link and extending downwardly therefrom, flanges along opposite sides of said arm extending transverse thereto, a lead screw supported in said flanges for rotation about an axis parallel to and externally offset below said lower link, said arm having a guide slot therein paralleling' said lower link, a follower mounted on said screw and disposed at one side of said arm, a guide block disposed on the other side of said arm, and a locking screw extending through said follower and said slot and into said block for attaching the block to the follower and for selectively locking the block to the arm, and means attaching the lower end of said spring to said block.

References Cited in the file of this patent UNITED STATES PATENTS 

